1. Field of the Invention
The present invention relates to a laser-drive-current control circuit for controlling the power of a laser applied to an optical disk, and an optical disk device provided with the laser-drive-current control circuit.
2. Background Art
Conventional optical disk devices can identify various optical disk media and carry out reproduction and recording operations suitable for each medium. For example, the reading power, erasing power and recording power of the laser diode differ among read-only media including CD-ROM and DVD-ROM, recordable media including CD-R and DVD±R, and rewritable media including CD-RW, DVD±RW and DVD-RAM. The optical disk devices have to control the drive current of the laser diode.
For example, a conventional optical disk device has means of identifying each optical disk medium loaded thereto, means of automatically setting the recording (and reproducing) data transfer rate suitable for the identified medium, and means of automatically setting the disk rotation speed suitable for the identified medium (see Japanese Patent Laid-Open No. 2003-141735).
Configured as described above, the optical disk device can automatically set the recording/reproducing transfer rate (and the rotation speed) suitable for the loaded recording medium, record and reproduce video data at high speed and reduce power consumption of the system.
As described above, there are a wide variety of optical disk media standards, and the laser light emission pattern for recording varies with specifications. In addition, even under the same standard, the laser light emission pattern varies with the type of the medium (such as a write-once-read-many medium and a rewritable medium). In addition, the laser light emission pattern varies with the recording speed.
The conventional technique described above is not designed to control the laser power and has a problem that the laser power cannot be controlled to accommodate such a wide variety of laser light emission patterns.